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Flashcards in Volcanic hazards (with case studies) Deck (25)
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1
Q

What is an Ocean Ridge?

A
  • Formed when plates move apart (constructive) in oceanic areas
  • Space between plates fills with basaltic lava from ridge below
  • Volcanic activity occurs from these ridges forming underground volcanoes which sometimes rise above sea level
2
Q

What is a Rift Valley?

A
  • Formed when plates move apart (constructive) on continental areas
  • Areas of the crust fall down between the fault lines a rift valley is formed, part between 2 valleys is called the horst
    e. g East Africa
3
Q

What are Deep Sea Trenches?

A
  • Where oceanic and continental plates meet, the denser oceanic plate goes under the continental (subduction)
  • Downwarping of oceanic plates forms a deep trench
    e. g Peru/Chile trench
4
Q

What are Young Fold Mountains?

A
  • Formed when 2 continental plates come together
  • Their edges and the sediments between them are forced up into fold mountains
  • Material is also forced downwards to form deep mountain roots
    e. g Himalayas
5
Q

What is Constructive plate margins?

A

2 plates moving apart

6
Q

What is Destructive plate margins?

A

2 plates moving towards each other

7
Q

What is Conservative plate margins?

A

2 plates moving alongside each other.

8
Q

What are Island Arcs?

A
  • As one plates goes under the other its get hotter due to friction and surrounding and melts
  • The material becomes less dense and rises to surface as pluntons of magma
  • When reach surface form volcanoes and a line of volcanoes form
9
Q

What is Ridge push?

A
  • Force that acts away from the ocean ridge

- Result of gravity acting down the slope of the ridge

10
Q

What is Slab pull?

A

-Pulling force exerted by cold, dense oceanic plunging into mantle due to its own weight

11
Q

What is Tephra?

A

Solid matter ejected by volcano e.g volcanic bombs, ash

12
Q

What is a Pyroclastic flow?

A
  • Know as ‘nuees ardentes’
  • Mixture of hot gas and tephra (over 800C)
  • Flow down sides of mountain of up to 700 km per hour
13
Q

What are the layers of the earth

A

Crust (lithosphere)
Mantle (asthenosphere)
Outer core (liquid)
Inner core (solid)

14
Q

Where can volcanoes occur?

A
  • Ocean ridges
  • Subduction zones (island arcs)
  • Rift valleys
  • Hot spots
15
Q

What is a hot spot?

A
  • In certain places the concentration of radioactive elements causes a hot spot to develop
  • From this a plume of magma rises to eat into the plate above to form active volcano
  • As the plates moves the hot spots stays forming a line of volcanoes
    e. g Hawaiian islands
16
Q

Name the primary effects of volcanic activity

A
  • Tephra
  • Pyroclastic flows
  • Lava flows
  • Volcanic gases
17
Q

What gases are released by a volcano eruption

A
  • Carbon dioxide
  • Sulphur dioxide
  • Carbon monoxide
  • Hydrogen sulphide
  • Chlorine
18
Q

Name the secondary effects of volcanic activity

A
  • Lahars (volcanic mudflows)
  • Flooding (melts glaciers)
  • Volcanic landslides
  • Tsunamis
  • Acid rain (from gases)
  • Climate change
19
Q

What are impacts upon humans by volcanic activity?

A
  • Death and injury
  • Destroying infrastructure
  • Ruining agriculture
  • Blocking roads and airlines
20
Q

Which LIC was affected by a volcanic event?

A

Congo
Mt Nyiragongo, (African rift valley)
January 2002

21
Q

What were effects of the Congo eruption?

A
  • 147 died, contaminated water, collapsing buildings, inhaling smoke
  • Thousands required medical attention
  • 350,000 people fled
  • Destroyed 1/3 of Goma which has over 200,000 inhabitants
  • Covered northern third of runway at Goma airport
  • Water and power supplies shutdown
  • Destroyed businesses (led to massive unemployment)
22
Q

Response to Congo eruption

A
  • ‘red alert’ (full evacuation)
  • 2 days in the UN ferried humanitarian aid e.g food, water, shelter, blankets, healthcare (cost $15 million)
  • UN set up camps to house people
23
Q

Which HIC was affected by a volcanic hazard?

A

Iceland
Eyjafjallajokull (mid-Atlantic ridge)
April 2010

24
Q

Effects of Iceland eruption?

A
  • Huge amounts of ice were melted causing floods to rush to nearby rivers, 1000 people evacuated
  • Large quantities of ash poured from volcano
  • Jet stream carried ash over Europe shutting down air traffic (cost £130 mil per day for 6 days)
  • Largest shutdown since world war 2
25
Q

Risks of Iceland eruption

A
  • Little risk as few lived in this part of Iceland

- Threat came from ash